# What is the difference in hydrogen ion concentration comparing solutions with a pH of 2 and pH of 4?

Sep 7, 2016

A hundred fold difference in ${H}_{3} {O}^{+}$ concentration applies

#### Explanation:

$p H = - {\log}_{10} \left[{H}_{3} {O}^{+}\right]$. And thus each $p H$ unit represents a tenfold difference in $\left[{H}_{3} {O}^{+}\right]$, i.e. hydrogen ion concentration.

Thus if $p H = 2$, $\left[{H}_{3} {O}^{+}\right] = {10}^{- 2} \cdot m o l \cdot {L}^{-} 1$ $=$ $0.01 \cdot m o l \cdot {L}^{-} 1$

And if $p H = 4$, $\left[{H}_{3} {O}^{+}\right] = {10}^{- 4} \cdot m o l \cdot {L}^{-} 1$ $=$ $0.0001 \cdot m o l \cdot {L}^{-} 1$.

Thus when $p H = 2$, $\left[{H}_{3} {O}^{+}\right]$ is $100 \times$ more concentrated than when $p H = 4$.